The two newest pups will both watch certain things on TV. No rhyme or reason for what catches their eye and they don't always get attracted to the same thing. The little girl (Maddie), especially, will watch quite intently sometimes.

Izzy, the oldest, barks like crazy at TV/video doorbells and of course that gets everyone else all wound up. Like @buffalobo we don't even have a doorbell and never have since Izzy's been around. I have no idea what made her start alerting to that noise.